Antennas are used in a variety of radio frequency communications and, as such, exist in a variety of shapes and sizes. Additionally, antennas may be configured from a variety of materials, such as copper, aluminum, and even certain dielectric materials. For example, antenna design generally requires that an antenna's shape and/or size directly relate to the frequency for which it is to be used. In other words, a particular communication system may operate at a predetermined frequency, the value of which is used in the computation of the antenna's shape and size.
Higher frequencies generally require smaller antennas for adequate gain, whereas lower frequencies generally require larger antennas for adequate gain. In this regard, antennas that are specifically designed for a particular frequency provide an initial means for filtering a signal by attenuating signals outside the desired range of communications. However, the rigid nature of antenna design can make communication schemes less flexible.
Modern cellular telephony is one area where flexible communication schemes may be desirable. For example, many different standards and frequency ranges now exist in cellular telephony, such as Code Division Multiple Access (CDMA) cellular telephony which may operate at the 1.9 GHz range, and Global System for Mobile (GSM) cellular telephony which may operate at the 900 MHz and 1.8 GHz frequency ranges. Since space is limited in cellular phones, having a single antenna configured with a cellular telephone that would communicate with such a variety of communication standards would allow a cell phone user to communicate with a variety of phone service providers. For example, a cell phone user in the United States possessing a cell phone with flexible communications capabilities and communicating via the Personal Communications Services (PCS) standard may be able to switch and communicate via the GSM standard using the same cell phone while traveling to Europe.
Antennas that are suitable for flexible communication schemes (e.g., a wide range of frequencies) may enable mobile devices to operate with other forms of communication systems. For example, present cellular telephones are also being configured with a relatively large amount of processing power, which enables them to function as more than merely telephones. This processing power could be used to deliver other forms of communication, such as from broadcast television and radio stations. Television broadcasts are commonly transmitted at ultrahigh frequencies (UHF), such as between 474 MHz and 798 MHz. A variety of antennas exist which can be used to receive signals on such frequencies; however, such antennas are generally large, inefficient, and not configurable with mobile devices.
It is against this background that the tunable antennas for mobile handsets disclosed herein have been invented.